Cooling means for an exposure cylinder of photoprinting apparatus



F. P. A. BLATTER 3,433,566 COOLING MEANS FOR AN EXPOSURE CYLINDER 0F PHOTOPRINTING APPARATUS Sheet March 18, 1969 iled July 27 19 5 INVENTOR FHA NCISC U5 PA. BLATTE'R ATTORNEY March 18. 1969 F. P. A. BLATTER COOLING MEANS F OR- AN EXPOSURE CYLINDER OF PHOTOPRINTING APPARATUS Filed July 27, 1966 Sheet 15/11/11111/1/1415???952. Fizz/4E2? m INVENTOR FRANCICUS RA. BLATTER BY WC.

ATTORNEY United States Patent 3,433,566 COOLING MEANS FOR AN EXPOSURE CYLINDER OF PHOTOPRINTING APPARATUS Franciscus Petrus Albertus Blatter, Venlo, Limburg, Netherlands, assignor to Chemische Fabriek L. van-der Griten N.V., Venlo, Netherlands, a corporation of the Netherlands Filed July 27, 1966, Ser. No. 568,241 Claims priority, application Netherlands, Aug. 2, 1965,

6510002 US. Cl. 355110 Int. Cl. G03b 27/10 9 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a photoprinting apparatus provided with an exposure cylinder, enclosing one or more tubular copying lamps, and having an air-distributing duct with air orifices within the cylinder for internally cooling the cylinder.

A part of the energy which is consumed by the lamps which are normally used in photoprinting apparatuses is converted into heat. Consequently the exposure cylinder of an apparatus of this kind is heated. In order to prevent the temperature of the cylinder from increasing to such an extent that the photoprinting material suffers from heating when it contacts the surface of the cylinder during exposure it is necessary to cool the cylinder. For this purpose several methods are known.

In apparatuses in which lamps of a comparatively small capacity are used, cooling air is often supplied and propelled through the cylinder with the aid of a fan which is mounted in the vicinity of one of the ends of the cylinder. In apparatuses with lamps of greater capacity usually a system is employed which comprises an air-distributing duct which is mounted within the cylinder and which is coupled to a fan via a pipe system. The cooling air which is supplied via such a duct spreads within the cylinder and escapes past the ends of the cylinder. A construction of this kind is known in which a duct is used both ends of which 'are coupled to the fan and whose diameter regularly decreases from the ends of the middle of the duct. In this system the direction of flow of the air in the duct is opposite to the direction in which the escaping air flows through the cylinder. As a consequence of the varying diameter of the duct the space along which the air can escape decreases in the direction towards the ends of the cylinder.

For a reliable functioning of a photoprinting apparatus it is extremely important that the cylinder is evenly cooled. If the cooling is uneven, so that zones with different surface temperatures are formed on the cylinder, these zones may become visible as darker or lighter parts respectively on the manufactured photocopies. With the cooling devices known up to the present the desired eveness of cooling can only be achieved with the aid of rather unattractive provisions, such as the use of elaborate pipe systems. In order to avoid the disadvantages of uneven cooling fans of relative high capacity are also often used, which 3,433,566 Patented Mar. 18, 1969 cool so strongly that unevenness of the cooling has no adverse effect on the photocopies. The noise caused by such fans, however, is often found annoying in practice.

It is the object of the present invention to provide a device which is simply constructed and affords very even and intensive cooling and which requires only a small quantity of energy for the cooling action. To achieve this object, a photocopying apparatus of the type referred to comprises an air-distributing duct having air orifices located within the cylinder, said air-distributing duct, at least for a considerable part of its entire length, in the longitudinal direction having a regularly diminishing width of passage, at its widest end being coupled to a device supplying cooling air and at its narrowest end being closed, and the cylinder being provided with an air outlet only at the end adjacent to the narrowest end of the duct.

The passage for the air flowing through then has nearly the same dimensions throughout, because wherever a smaller quantity of air is passing through, a narrower passage is available, and wherever a larger quantity of air is passing through, a wider passage is available. The airdistributing duct may thus be of very simple construction, e.g. a substantially conical, air duct of sheet metal. Because only a small quantity of ventilating energy is necessary, the noise is insignificant.

In a preferred form of apparatus according to the invention the space within the cylinder is divided, by means of a substantially flat plate which is axially mounted in that space, into two compartments which communicate via slits which are left along the whole length of the plate between the edges of the plate and the wall of the cylinder, the copying lamp(s) being accommodated in one compartment, while the air-distributing duct is located in the other compartment and has as a separating wall a gradually decreasing part of the plate, in which the orifices have been provided. In this situation on the one hand the light is effectively screened on the operators side, on the other hand the air escapes through the slits along the wall of the cylinder towards the compartment in which the duct is located. A strong whirling, and accordingly a good cooling action, is achieved. The duct with transverse dimensions regularly decreaseing towards the air-outlet end of the cylinder oifers only little resistance to the escaping air, in spite of the fact that the quantity of such air increases towards the air-outlet end.

The invention will now be further explained with reference to the accompanying drawing, in which:

FIGURE 1 is a view of an exposure cylinder, shown in perspective and partly opened, with an air-distributing duct and a lamp mounted therein, and

FIGURE 2 is a longitudinal section of this cylinder and adjacent parts along the line IIII in FIGURE 1.

The glass cylinder 1 of a photoprinting apparatus (which is not shown further), is rotated around its axis by its contact with moving conveyer belts. A lamp 2, which produces actinic light, is mounted almost in the centre of the cylinder and is fixed to the apparatus, so that it does not rotate with the cylinder.

Extending alongside the lamp 2 is a fiat plate 3, which leaves a slit 4 along the inner wall on either side of the cylinder.

The plate 3 divides the space inside cylinder 1 into two compartments, which do not differ much in volume. In the plate 3 is a row of air orifices 5, which are all the same size. Together the slits 4 have a total width of passage which is larger than that of the orifices 5.

Fixed against the plate 3 is a curved plate 6, which forms part of an oblique cone, as is clearly shown in FIGURE 1. At the right end (as illustrated) this plate 6 is located throughout at a short distance along the inner wall of the cylinder 1, this distance radially having the same dimension as the slits 4. Up to its other end the plate 6 is attached to the upper edge of the plate 3, while it gradually recedes further from the lower edge of plate 3 and gradually leaves this plate free. At the left end (a shown), the air-distributing duct, which is formed by the plates 3 and 6, is shut olT by a wall 7 (FIGURE 2).

In FIGURE 2 supporting rolls 8 for supporting cylinder 1 are shown, which are carried by walls 9 and 10 of the apparatus. Fitted against the right wall, as seen in FIGURE 2, is the air duct of a fan 12 for cooling the cylinder. The duct 11 is shaped in such a way that the fan only blows air into the duct formed by the plates 3 and 6. At the left end of the cylinder, as seen in FIG- URE 2, an opening has been made in wall 9 and an air outlet duct 13 the cross-section of which is equal to that of cylinder 1 has been provided, which connects up exactly with the cylinder. The device operates as follows:

During the rotation of the cylinder 1 and the burning of the lamp 2 a quantity of heat is generated, which has to be partly removed by even cooling. For this purpose the fan 12 via the duct 11 blows air into the duct formed between the plates 3 and 6. Through the holes this air gradually enters the compartment in which the lamp 2 is located. From there this air partly flows through the slits 4 into the compartment on the other side of the plate 3. Thus an equal and evenly distributed quantity of air is fed to every part of the cylinder, which air, after having been warmed up, does not interfere with the cooling of cylinder parts which are located further downstream, but for the greater part escapes to the other side of the plate 3 through the slits 4. The width of passage of the duct formed between the plates 3 and 6 is throughout amply suflicient for the quantity of air flowing through the duct, which decreases in the direction of flow of the air, whilst the air leaving this duct can flow away through a part of the cylinder whose cross-section gradually increases towards the downstream end. It has been found that in this manner it is possible to achieve a suflicient as well as an entirely even cooling of the cylinder with a small fan.

In the embodiment described above, cooling air is only supplied via the wide end of the air-distributing duct. It has, however, been found that a particularly effective cooling, which can also be used for lamps with a very high capacity, can be achieved when cooling air is blown not only into the duct, but also directly into the cylinder end which is adjacent to the wide end of the duct. In that case a main stream of cooling air is formed, which moves axially through the cylinder compartment in which the lamp is mounted. Tangentially directed streams of fresh air are constantly added to this main stream via the holes in the duct. These streams bring about an intensive whirling of the main stream, while each of the added streams displaces a part of the main stream towards the compartment located behind the plate. Thus the main stream, with its axial velocity remaining almost constant, maintains a practically equal volume and a practically equal temperature, owing to which very oven cooling is achieved, which moreover is very effective owing to the whirling of the main stream. The quantity of air which is displaced towards the compartment behind the plate gradually increases on its way to the outlet end. However, as it gets gradually more space to flow through, owing to the decreasing cross-section of the duct, this air can easily escape.

What I claim is:

1. In photoprinting apparatus comprising an exposure cylinder adapted to enclose tubular copying lamp means extending longitudinally inside the cylinder and means for blowing cooling air into one end of said cylinder, its other end being open for the passage of air therefrom, means inside said cylinder for distributing the air inflow substantially evenly about and along the region of said cylinder occupied by said lamp means and then passing the air out of said other end, comprising an air duct having a mouth at said one end to take in at least part of said air inflow and extending lengthwise of said cylinder and, through at least a major part of its length, progressively diminishing in cross-sectional passage area in the direction toward said other end, said duct being provided with orifice means opening laterally therefrom into said region and distributed substantially evenly therealong for delivering said at least part of said air inflow into said region substantially evenly over the length thereof.

2. Apparatus according to claim 1, said orifice means being directed tangentially into said region to effect whirling movement of the air therein.

3. Apparatus according to claim 1, said air blowing means being arranged relative to said one end so as to supply substantially all of said air inflow into the mouth of said duct.

4. Apparatus according to claim 1, said air duct being located to one side and said lamp means to the other side of the space inside said cylinder, said air blowing means being aligned with said one end of said cylinder so as to supply a part of said air inflow into the mouth of said duct and another part of said air inflow directly into and along the regions of said cylinder occupied by said lamp means.

5. Apparatus according to claim 1, said air distributing means further including partition means dividing the space inside said cylinder longitudinally into two compartments, said lamp means being in one of said compartments and said duct being in the other, said partition means having upper and lower edges thereof spaced from the wall of said cylinder to provide therealong slits for passing air from said one compartment into the other.

6. Apparatus according to claim 5, the air passage area of said slits being at least as great as the air passage area of said orifice means.

7. Apparatus according to claim 5, said compartments being of nearly equal volume.

8. Apparatus according to claim 5, said partition means comprising a substantially flat plate disposed axially in said space and forming a Wall of said duct, said orifice means comprising a series of openings formed in and along a portion of said plate near to one of said edges.

9. Apparatus according to claim 8, said duct being further formed by an elongate transverse curved plate having a substantially conical shape, said curved plate being fixed to said substantially flat plate so as to encompass said openings and with its wider end forming said mouth at said one end of said cylinder, its narrower end being closed.

References Cited UNITED STATES PATENTS 2,196,400 4/1940 Schwarzmayr 8824 2,821,126 1/1958 Heller 8824 2,979,986 4/1961 Miller 8824 3,307,465 3/1967 Adair 77.5 3,329,076 7/ 1967 Bishop 95--77.5 3,361,047 6/1965 Breuers 95-77.5

FOREIGN PATENTS 522,411 3/1956 Canada.

NORTON ANSHER, Primary Examiner.

C. B. FUNK, Assistant Examiner.

US. Cl. X.R. 

